1. Field of the Invention
This invention relates to the field of power transmissions in general, and in particular, to a lubrication system for a chain for transmitting power from a driving shaft to a transmission shaft disposed parallel to the driving shaft.
2. Description of Prior Art
Certain transmissions transmit power from a driving shaft (driven for example by an engine or another transmission) to a transmission shaft disposed parallel to the driving shaft and below the driving shaft, by means of a chain drive. In such transmissions, the interior of a chain case has been separated from the interior of the rest of the transmission case and an appropriate amount of a lubricating oil has been sealed in the chain case so that the lower end of the chain moves through the lubricating oil. This arrangement avoids the problems of too much oil flowing into the chain case from the exterior, but usually with the result that either excess oil collects in the chain case or too much chain-lubricating oil contained in the chain case flows out to the exterior, resulting in insufficient amounts of the oil remaining in the chain case.
Use of a sealed chain case as in the prior art has the drawbacks that the lubricating oil collected in the chain case is stirred by the chain, resulting in a rise in the oil temperature. A rise in the oil temperature causes deterioration of certain oil seal parts provided for the chain case and/or degradation of the viscosity of the lubricating oil itself, leading to insufficient lubrication of the chain and bearings and the associated structure. Although the rise in the oil temperature can be avoided by reducing the volume of the lubricating oil, so as to reduce the amount of the oil stirred by the chain, the reduction in the amount of the lubricating oil also causes the problem of premature deterioration of the oil.